Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 3 - By Alexander Von Humboldt And Aime Bonpland.
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(* Franklin's Journey To The Polar Sea Page 529.)
Where The Diorite, Partly Globular, Approaches The Green Slate Of
Malpasso, Real Beds Of Green Slate Are Found Inclosed In Diorite.
The
fine saussurite which we saw in the Upper Orinoco in the hands of the
Indians, seems to indicate the existence of a soil of euphotide,
superposed on gneiss-granite, or amphibolic slate, in the eastern part
of the Sierra Parime.
4. GRANULAR AND MICACEOUS LIMESTONE OF THE MORROS OF SAN JUAN.
The Morros of San Juan rise like ruinous towers in a soil of diorite.
They are formed of a cavernous greyish green limestone of crystalline
texture, mixed with some spangles of mica, and are destitute of
shells. We see in them masses of hardened clay, black, fissile,
charged with iron, and covered with a crust, yellow from
decomposition, like basalts and amphiboles. A compact limestone
containing vestiges of shells adjoins this granular limestone of the
Morros of San Juan which is hollow within. Probably on a further
examination of the extraordinary strata between Villa de Cura and
Ortiz, of which I had time only to collect some few specimens, many
phenomena may be discovered analogous to those which Leopold von Buch
has lately described in South Tyrol. M. Boussingault, in a memoir
which he has recently addressed to me, calls the rock of the Morros a
problematic calcariferous gneiss. This expression seems to prove that
the plates of mica take in some parts a uniform direction, as in the
greenish dolomite of Val Toccia.
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